I have an HTML document that uses multiple style tags. One of those styles has the following content
<style id='pstyle'>
.p0010, .p0016, .p0022, .p0028, .p0032,
.p0034, .p0038, .p0042, .p0044, .p0046,
.p0048, .p0050, .p0052, .p0054, .p0056,
{
max-width:100%;
background-size:100%;
background-image: url('sprites.png');
}
</style>
document.styleSheets allows me to access the full set of stylesheets used by the document. From there - once I have grabbed the right stylesheet - I can use the cssRules array attribute to access the selectorText attribute of each contained style. However, I have been unable to figure out how to find the "right" style sheet. Whilst I can give the stylesheet an id this does not turn up as an attribute of the document.styleSheets[n] object.
I do a great deal of DOM manipulation but it is mostly with the visual elements in the document. I'd be much obliged to anyone who can tell me how I go about identifying the "right" stylesheet
A plain English version of the task
a. Find the style element - bearing in mind that there will be others - with the id pstyle
b. Read the class names defined therein and do whatever
I'm not sure to understand if you want to get the stylesheet associated with the <style> element, or if you want to retrieve the element from the stylesheet.
So here you'll get both :
// from the element
console.log(pstyle.sheet === document.styleSheets[2]);
// from the stylesheet
console.log(document.styleSheets[2].ownerNode === pstyle);
<style id='pstyle'>
</style>
note that in the snippet it's [2] because stacksnippet does inject stylesheets
And now to get the cssRules and selectorText, you just have to read it from the selected styleSheet:
var pstyle = document.getElementById('pstyle');
// from the element
console.log(pstyle.sheet.cssRules[0].selectorText);
// from the stylesheets
for(var sheet of document.styleSheets){
if(sheet.ownerNode === pstyle){
console.log(sheet.cssRules[0].selectorText);
}
}
<style id='pstyle'>
.p0010, .p0016, .p0022, .p0028, .p0032,
.p0034, .p0038, .p0042, .p0044, .p0046,
.p0048, .p0050, .p0052, .p0054, .p0056
{
max-width:100%;
background-size:100%;
background-image: url('sprites.png');
}
</style>
Related
Can I apply an external stylesheet to a specific div/element with shadow-dom or via any other means? I've heard about shadow-dom and I believe it lets you constrain your styles, but that's about all I know.
Specifically, I want half the page to use bootstrap, and the other half to use MUI or something else. This is just to show how my library works nicely with different themes.
I don't want to modify the CSS in anyway to constrain it to a specific element, nor do I want to use iframes.
Yes, you can apply an external stysheet in a Shadow DOM using the #import url CSS rule.
div.attachShadow( { mode: 'open' } )
.innerHTML = `
<style>
#import url( './external-style.css' )
</style>
<!-- other elements -->`
NB: The #import rule must placed at the top of the <style> element.
You can then manipulate the Shadow DOM like a normal DOM:
div.shadowRoot.appendChild( firstSection.cloneNode( true ) )
If your content is already existing in the normal DOM, you can move it with appendChild(), duplicate it with cloneNode() as in the above example), or reveal it with the help of <slot> element:
div1.attachShadow( { mode: 'open' } )
div1.shadowRoot.innerHTML = `
<style>
:host { display: inline ; background: #cfc ; }
::slotted( span ) { color: red ; }
</style>
<slot></slot>`
<div id=div1>
<span>Hello</span> world
</div>
In the last case you'll need to use the ::slotted pseudo-element to change the style of the original DOM, so maybe you'll have to modify already existing stylesheet. The best solution depends on your use case.
I'm looking into custom CSS properties and have come up with the code below.
If I put the CSS inline using a STYLE attribute on the canvas tag (like this: style="--rgLinewidth: 3" ) then I can get the custom CSS values using the script shown below.
But using a tag, as below, then it doesn't show the custom CSS properties.
Is it possible to? And if so how?
<html>
<head>
<style>
canvas#cvs {
--rgLinewidth: 3;
background-color: red;
}
</style>
</head>
<body>
<canvas id="cvs" width="600" height="250">[No canvas support]</canvas>
<script>
canvas = document.getElementById("cvs");
styles = window.getComputedStyle(canvas);
alert(styles.getPropertyValue('background-color'));
alert(styles.getPropertyValue('--rgLinewidth'));
for (var i=0; i<styles.length; i++) {
if (canvas.style[i].indexOf('--rg') === 0) {
var value = styles.getPropertyValue(canvas.style[i]);
alert([canvas.style[i], value]);
}
}
</script>
</body>
</html>
It does not work because you query for computed style and then attempt to retrieve values of corresponding properties from the inline style, where they do not exist -- your canvas does not define an inline style. You need to query the values through the same styles object where you find the properties.
Consider the following function which when passed an element, will search through its computed style and return the value of the first CSS variable whose name starts with --rg:
function find_first_rg_value(el) {
var styles = getComputedStyle(el);
for (var i = 0; i < styles.length; i++) {
if (styles[i].startsWith('--rg')) {
return styles.getPropertyValue(styles[i]);
}
}
}
(Use like find_first_rg_value(canvas))
The difference between my approach and yours is, as I said, that you attempt to fetch the value from canvas.style[i], but canvas.style is effectively empty. Use styles instead.
Computed style (getComputedStyle), as the name implies, contains "summary" style computed per CSS cascading, inheriting, and so on, with inline style, if any, applied on top (overriding priority). Assigning inline style therefore affects the computed style, but querying inline style only gives you inline style you assigned, no more.
This means that in most cases like yours one would want to use getComputedStyle. Additionally, since CSS variables cannot be queried using style.fontName syntax, you need to use getPropertyValue function for these (all dashes intact in the passed property name), regardless if you are dealing with an inline or computed style object.
For example, you can change the ink colour in paper-tabs by changing --paper-tab-ink: var(--accent-color);. Is it possible to change the value of the CSS custom properties dynamically similar to how you can toggle a class or change the style in JS?
There are different ways to do this, but a simple answer is to use the Polymer.updateStyles() method after making your class changes.
For example, let's say your styles are:
<style>
.yellow x-example {
--light-primary-color: #fdd85f;
}
.red x-example {
--light-primary-color: red;
}
</style>
and you want to make the component use the styles in the .red class. You simply add it as you normally would in javascript, then be sure to also use this function to actually update it on the page.
<div class="yellow" onclick="this.className='red'; Polymer.updateStyles()">
<x-example></x-example>
</div>
Yes, first get the object of your custom element. Then get the customStyle object. Add a style to that object. And then run element.updateStyles();
t.clickListener= function(e) {
var t = Polymer.dom(e).localTarget; //retarget if needed
t.customStyle['--the-color-etc'] = 'pink';
t.updateStyles(); // mandatory for the CSS variables shim
};
See the docs
On a web page that contains an eternal CSS style sheet (loaded via <link rel="stylesheet">), I would like to modify the selector of one of its CSS rules. I can reference the rule with:
var rule = document.styleSheets[…].cssRules[…];
(where … are numbers).
Once selected, I can read its selector and other values:
rule.cssText // 'em { color: red }'
rule.selectorText // 'em'
rule.style.color // 'red'
However, when I try to write one of these, it only lets me write the style object:
// These won’t work
rule.cssText = 'em.foo { color: red }';
rule.selectorText = 'em.foo';
// This will work
rule.style.color = 'blue';
Why doesn’t it let me write .cssText or .selectorText? From what I see in the spec, they are not readonly.
Update: I’ve checked for inline style sheets, too. It doesn’t work either.
At least Firefox implements them read-only.
https://developer.mozilla.org/en-US/docs/Web/API/CSSRule.cssText
https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleRule/selectorText
I'm creating a span in my web page with dojo.create, and need to apply CSS to it. I can see how to apply a style to it in the dojo reference, but I'd rather apply it via the external stylesheet (there's quite a few attributes I need to set and I'd rather not do it inline).
So given the example code below, how would I apply the CSS for the printSpan class?
var node = dojo.create("span", {innerHTML:_text, id:"printSpan", class:"printSpan"}, map);
You can write this in your external stylesheet:
.printSpan { color: red; }
This is called the class selector.
By the way, your code should be:
{ innerHTML : _text, id : "printSpan", "class" : "printSpan" }
Notice the colon was inside the "class" string, though it should be outside and printSpan is a different string.